cellular structure and ion

8/2/2019 Cellular Structure and ion

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CellsWhat are cells?

The basic unit of structure and function in organisms

StructureThis refers to the manner of construction of something

and the arrangement of its parts in other words how

it is built.

FunctionWhat something is used for or in other words how

something works or does

We see a very high correlation between structure andfunction in almost all things, e.g A fish has fins andgills (structure) that enables it to swim and breath(functions) under water


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Prokaryotic and Eukaryotic cellsThere are two types of cells:

Prokaryotic cellsEarliest cellsLack membrane bound organellesNo nucleus

No mitochondriaHave membrane, cytoplasm & free DNAEukaryotic cellsMay have evolved from Prokaryotic

Have a nucleus that holds the DNA inside a membraneHave mitochondriaAlso have cell membrane & cytoplasm


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plant cells and animal cells

All organisms are constructed bycells

There are two main types of cells, plant cells and animalcells.

Most cells are so small that you can see them onlywith the help of a microscope.

All cells come only from other cells.

Living things is diverse but all cells share commoncharacteristics

Cells are composed of one cell unicellular or morecells multicellular.


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Using the microscopes to see cells

There are two types of microscopes, the light microscopeand the electrone microscope

Photographs of what is seen through a microscope arecalled micrographsor photomicrographs:

Light microscope

Magnifies X 1500

Light micrographsshow what can be seen with a lightmicroscope.

Electron microscopeMagnifies X 200 000

Electron micrographsshow what can be seen with anelectron microscope.


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Why not?

Cells are small so they can exchange materials withtheir surroundings.Surface area relative to the volume decreases as sizeof cell increases.

Cell size is limited because as the size of the cellincreases the less the cells ability to take in nutrientsand remove waste products .

Here is how it works!

Are there cells the size of an Elephant?


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Cell surface volume ratio


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Sizes of living things


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The general structure of a plant

Cell wall

Cell surface membrane

Cytoplasm

MitocodriaNucleus

Vacuole containing cell sap

Starch granule

Nuclear membrane


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Ultra stucture of a plant cellThis structure is what is observed at about X 200 000 under

an electron microscope cell organelles can be identified.

Cell wall


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The two pictures

(micrographs) shows howA plant cell looks likeunder a light microscope.

NoticeThe cell wallThe nucleus, one of the

dark circles near the

cell wall.The chloroplasts, the

rest of the circles.The large vacuole which

appears inside the cell.

Light micrograph of some plant cells


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The general structure of an animal cell

Cell surface membrane

Cytoplasm

Vacuole containing cell sap

Nucleus

Nuclear membraneMitocodria

Notice

How small the vacules arecompared to the plant cell.

The absence of the cell wall The irregular chape of the cell compared to the regular

plant cell.


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Ultra stucture of an animal cellThis structure is what is observed at about X 200 000 underan electron microscope, cell organelles can be identified.


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The structure of plant and animal cells

Here are the common features in all cells Cell surface membrane: a thin membrane that separates

the cell contents from the surrounding. The cytoplasm: a jelly-like liquid which contains a

mixture of proteins, and other substances. The nucleus: surrounded by a nuclear membrane and

contains genetic material. Vacuoles: structures in the cytoplasm that contain

fluid, usually larger in animal cells than in plant cells.

These are the differencesPlant cells have a cell wall that surrounds the cell chloroplasts which are responsible for producing

chlorophyll the green pigment seen in plant leaves and

stems.


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Functions and structures

1 Cell Membrane:Semi-permeable,

controls what enters and leaves the cell, outercontainment envelope.


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Cytoskeleton: A microscopic network of actin filaments

and microtubules in the cytoplasm of many living cellsthat gives the cell shape and coherence or simplygives structure to a cell.

2 Nucleus: control center for activities & reproductionof the cell, DNA & chromosomes are housed here.

Nucleolus: contains and makes RNA

Chromosome: coiled DNA: contains instructions forcharacteristics of an organism.

Chromatin: protein composing of chromosomes



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Nucleus and nuclear envelop


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Nuclear membrane

protects and controls whatgoes in and out of the nucleus

It is made up of two

membranes with a narrowspace between them.

The membranes have smallopenings called nuclear pores.

(notice the nuclear pores inthis picture of a nucleus)


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3 Ribosomes: Ribosomes are composed of a large

subunit and a small subunit which are small beads ofRNA (ribonucleic acid).

Site of Protein Synthesis on the E.R. Ribosomes are made in the nucleolus of the nucleus They move from the nucleus to the cytoplasm They then attach to the surface of the endoplasmic

reticulum Once attached they make proteins, both for the cell

itself and for export to other cells.

The ribosomes are therefore found on theendoplasmic reticulum were they perform their

functions in protein synthesis.


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4 Endoplasmic reticulum (ER) is a system of membranouschannels which run from the nuclear envelope to the cellsurface membrane.

The are two types of endoplasmic reticulum ER

Rough ER is studded with ribosomes and is the site of proteinsynthesis and processing.

Smooth ER lacks ribosomes and is the site of synthesis ofphospholipids and the packaging of proteins into vesicles,among other functions.

The functions of the endoplasmic reticulum are to Transport RNA from the nucleus to the ribosomes

Provide a very large surface area for attachment ofribosomes

Provide trans ort for roteins that the ribosomes roduce



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Proteins made by the ribosomes are:

Pushed through the ER membrane into the tunnels ofthe ER

Enclosed in bits of the smooth ER membranes whichthen get pinched off to form small transport vesicles

Then carried by these transport vesicles through thecytoplasm to the golgi bodies.

The Golgi apparatus specializes in the production &transport of lipids and membrane proteins

Rough ER has ribosomes

Smooth ER lacks ribosomes



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5 The Golgi bodies

The Golgi apparatus consists of a stack of curvedchannels.

The Golgi bodies perform the following functions

Receives protein and also lipid-filled vesicles fromthe ER,

packages, processes, and distributes them within

the cell. This organelle may also be involved in secretion by

producing lysosomes by sealing off digestiveenzymes in packets of membrane.

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6 Lysosomes are vesicles produced by the Golgi

apparatus.Lysosomes have the following functions

Contain hydrolytic enzymes

Are involved in intracellular digestion.

7 Vacuoles (large) and vesicles (small) are membranoussacs in the cell that store substances.

Store water, sager and other substances in the cellsap

To help keep the cell firm (turgid)


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8 Chloroplasts

These are bound by two membranes enclosing a fluid-filledstroma that contains enzymes.

Membranes inside the stroma are organized into

thylakoidsthat house chlorophyll.

Chlorophyll absorbs solar energy and carbohydrates aremade in the stroma.

the main function of chloroplasts is to make food duringphotosynthesis.



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Functions and structures9Thetonoplast is the membrane separating the cell

vacuole from the cytoplasm. It controls what moves in

and out of the vacuole

10 The mitochondriaTheseare found in plant and animal cells.

Mitochondria are bounded by a double membranesurrounding fluid-filled matrix.

The inner membranes of mitochondria are cristae.

The matrix contains enzymes that break downcarbohydrates and the cristae house proteincomplexes that produce ATP.

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10 The mitochondria


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Plant cells

Plant cells have different structures than animalcells

Plant cells have something called a CELL WALL whileanimals do not.

Plant cells have an organelle called a CHLOROPLASTthat takes energy from the sun and converts it intosugars.

Does your body make sugar from the sun or do youget it from food?


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Animal cells organize the body. You have brain cells,stomach cells, bone cells, and many other types ofcells. Each is different from the others.

Nerve cells conduct electrical impulses through thebody. There are cells in your intestine that absorbnutrients from the food you eat. Stomach cellssecrete an acid to digest your food

Do you think that your skin cells can absorb thenutrients from your lunch? Why not?

Animal cells

cellular structure and ion

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